Iron-and copper-containing metalloproteins are of particular importance in catalyzing electron transfer and oxidation-reduction reactions in biological systems. Our work has concentrated on the use of electronic and resonance Raman spectroscopy as a means of identifying metal ion ligands and the stereochemistry of metal ion binding within the proteins. As an example, we have been able to demonstrate a new class of metalloproteins, the iron-tyrosinate proteins, which are characterized by the appearance of tyrosine ring vibrational modes in their resonance Raman spectra. Since the resonance Raman effect arises from an interaction of vibrational and electronic energy states, the Raman observations must be due to the occurrence of tyrosinate yields iron charge transfer transitions in the electronic absorption spectra of these proteins. We have shown that the iron-tyrosinate category includes the enzyme, protocatechuate 3,4-dioxygenase, as well as the iron-binding proteins, transferrin and lactoferrin. The proposed research focuses upon structural clarification in several other classes of iron-containing proteins including the iron-dimer proteins, hemerythrin and ribonucleotide reductase; the iron-sulfur protein, xanthine oxidase; and the iron-uptake siderophore, schizokinen. Information will also be sought on the molybdenum and flavin sites in xanthine oxidase and on the blue copper site in azurin. Structural assignments will be made on the basis of heavy atom substitutions, normal coordinate analyses, excitation profiles, and reference to model compounds. Our goal is to elucidate the active site configurations of these proteins and their relationship to other metal-containing proteins as a means for understanding the biological function of metalloproteins at the molecular level.